using System;

using Org.BouncyCastle.Crypto.Parameters;

namespace Org.BouncyCastle.Crypto.Generators
{
	public class DesEdeKeyGenerator
		: DesKeyGenerator
	{
		public DesEdeKeyGenerator()
		{
		}

		internal DesEdeKeyGenerator(
			int defaultStrength)
			: base(defaultStrength)
		{
		}

		/**
		* initialise the key generator - if strength is set to zero
		* the key Generated will be 192 bits in size, otherwise
		* strength can be 128 or 192 (or 112 or 168 if you don't count
		* parity bits), depending on whether you wish to do 2-key or 3-key
		* triple DES.
		*
		* @param param the parameters to be used for key generation
		*/
		protected override void engineInit(
			KeyGenerationParameters parameters)
		{
			this.random = parameters.Random;
			this.strength = (parameters.Strength + 7) / 8;

			if (strength == 0 || strength == (168 / 8))
			{
				strength = DesEdeParameters.DesEdeKeyLength;
			}
			else if (strength == (112 / 8))
			{
				strength = 2 * DesEdeParameters.DesKeyLength;
			}
			else if (strength != DesEdeParameters.DesEdeKeyLength
				&& strength != (2 * DesEdeParameters.DesKeyLength))
			{
				throw new ArgumentException("DESede key must be "
					+ (DesEdeParameters.DesEdeKeyLength * 8) + " or "
					+ (2 * 8 * DesEdeParameters.DesKeyLength)
					+ " bits long.");
			}
		}

		protected override byte[] engineGenerateKey()
		{
			byte[] newKey;

			do
			{
				newKey = random.GenerateSeed(strength);
				DesEdeParameters.SetOddParity(newKey);
			}
			while (DesEdeParameters.IsWeakKey(newKey, 0, newKey.Length));

			return newKey;
		}
	}
}
